Catalytic hydrogenation is a fundamental reaction in chemistry, and is used in a large number of chemical processes. Catalytic hydrogenation of ketones and aldehydes are useful and indispensable processes for the synthesis of alcohols, which are valuable end products and precursor chemicals in the pharmaceutical, agrochemical, flavor, fragrance, material and fine chemical industries.1 
To achieve a catalytic hydrogenation transformation in the reduction of ketones and aldehydes, molecular hydrogen (H2) is used. However, for the hydrogenation process to proceed, a catalyst or catalytic system is needed to activate the molecular hydrogen.
Noyori and co-workers developed the versatile RuCl2(PR3)2(diamine) and RuCl2(diphosphine)(diamine) hydrogenation catalyst system that are highly effective for the hydrogenation of ketones.2 It was subsequently discovered that the Noyori catalysts were effective for the reductive hydrogenation of imines to amines.3 It has been reported that ruthenium aminophosphine complexes of the type RuCl2(aminophosphine)2 and RuCl2(diphosphine)(aminophosphine) are also very effective catalysts for the hydrogenation of ketones, aldehydes and imines, including the preparation of chiral compounds.4 Hence, these catalysts are a versatile alternative to the Noyori-type catalysts.
The complex RuCl2(aminophosphine)2 can be prepared using various methods. Refluxing a basic 2-propanol solution of [RuCl2(cod)] with stoichiometric amounts of the aminophosphine ligand results in the crystalline product. Refluxing a mixture of RuCl2(dmso)4 with two equivalents of the aminophosphine ligand in toluene also results in the catalyst. In addition, refluxing a mixture of RuCl3(PPh3)3 and greater than two equivalents of the aminophosphine ligand also results in an excellent yield of the bisaminophosphine product.
The synthesis of [RuCl(p-cymene)((R,Sp)-2-[1-(N,N′-dimethylamino)ethyl]-1-diphenylphosphinoferrocene)]Cl has been reported and it was found that these compounds are active for the transfer hydrogenation of ketones in basic 2-propanol solutions under refluxing conditions.5 